Two AT-Hook proteins regulate A/NINV7 expression to modulate sucrose catabolism for cold tolerance in Poncirus trifoliata

通讯作者：刘继红

通讯单位：华中农业大学

研究背景：

         Invertase (INV)-mediated sucrose (Suc) hydrolysis, leading to the irreversible production of glucose (Glc) and fructose (Frc), plays an essential role in abiotic stress tolerance of plants. 

The established regulatory module HATs/AHLs-A/NINV7 unveils a novel molecular framework by which plant may adapt to the cold stress by modulating Suc catabolism and sugar homeostasis, which will promote our understanding of the molecular events involved in IN V-mediated sucrose metabolism under cold stress.

         转化酶(INV)介导的蔗糖(Suc)水解导致不可逆的葡萄糖(GLC)和果糖(FRC)的产生，在植物的非生物胁迫耐性中起着至关重要的作用。通过建立的调控模块HATS/AHLS-A/NINV7揭示了一个新的分子框架，植物可以调节Suc的分解代谢和糖的稳态来适应低温胁迫，这将有助于我们理解冷胁迫下IN V介导的蔗糖代谢所涉及的分子事件。

研究内容：Previously, a cold-responsive A/NINV-encoding gene PtrA/NINV7 (formerly named as PtrA/NINV) from trifoliate orange (P. trifoliata L. Raf.), a widely-used rootstock for citrus. In the study, they investigated the molecular mechanism underlying transcriptional regulation of PtrA/NINV7 for cold-induced sugar metabolism. Two AHL proteins, PtrAHL14 and PtrAHL17, were identified to act as transcriptional activators of PtrA/NINV7 and modulate sugar contents in response to the cold stress. In addition, they demonstrated that PtrAHL14 and PtrAHL17 formed homo- and heterodimers, as well as interacted with histone acetyltransferases (HATs), leading to enhanced histone3 acetylation (H3ac) level and occupancy of RNA Polymerase II on PtrA/NINV7 promoter. 

       此前，一个冷反应A/NINV编码基因PtrA/NINV7(统称为PtrA/NINV)是从三叶橙(P.trifoliata L.Raf.)中获得的，三叶橙是一种广泛使用的柑橘砧木。在这项研究中，他们研究了PtrA/NINV7转录调控冷诱导糖代谢的分子机制。两个AHL蛋白PtrAHL14和PtrAHL17被鉴定为PtrA/NINV7的转录激活子，并调节糖含量以响应冷胁迫。此外，他们还证实了PtrAHL14和PtrAHL17形成同源和异源二聚体，并与组蛋白乙酰转移酶(HATS)相互作用，导致组蛋白3乙酰化(H3ac)水平增加和RNA聚合酶II在PtrA/NINV7启动子上的占位

研究结果：a cold-induced alkaline/neutral INV gene (PtrA/NINV7) of trifoliate orange was shown to function in cold tolerance via mediating the Suc hydrolysis. Meanwhile, a nuclear matrix-associated region (MAR) containing A/T-rich sequences within its promoter was indispensable for the cold induction of PtrA/NINV7. Two AT-Hook Motif Containing Nuclear Localized (AHL) proteins, PtrAHL14 and PtrAHL17, were identified as upstream transcriptional activators of PtrA/NINV7 by interacting with the A/T-rich motifs. PtrAHL14 and PtrAHL17 function positively in the cold tolerance by modulating PtrA/NINV7-mediated Suc catabolism. Furthermore, both PtrAHL14 and PtrAHL17 could form homo- and hetero-dimers between each other, and interacted with two histone acetyltransferases (HATs), GCN5 and TAF1, leading to elevated histone3 acetylation level under the cold stress.

      一个耐冷诱导的中性/碱性INV基因(PtrA/NINV7)通过调节蔗糖的水解性而在耐冷性中发挥作用。同时，在PtrA/NINV7的冷诱导过程中，其启动子内含有富含A/T序列的核基质相关区(MAR)是必不可少的。两个含有核定位(AHL)蛋白的AT-Hook基序PtrAHL14和PtrAHL17通过与富含A/T的基序相互作用被鉴定为PtrA/NINV7的上游转录激活因子。PtrAHL14和PtrAHL17通过调节PtrA/NINV7介导的Suc分解代谢，在耐冷性中发挥积极作用。此外，PtrAHL14和PtrAHL17都能相互形成同源和异源二聚体，并与两个组蛋白乙酰转移酶(HATS)GCN5和TAF1相互作用，导致冷胁迫下组蛋白3乙酰化水平升高。

图1. PTRA/NINV7的沉默减弱了柑橘的冻结耐受性

图2. PtrAHL14和PtrAHL17的过表达增强了转基因植物的耐冷性

原文链接：https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.18304

Journal:New Phytologist

Published date:  June 13, 2022